This invention relates generally to reclosable plastic bags and in particular to fastener assemblies for such bags, tape having reclosable fasteners thereon used in the manufacture of reclosable plastic bags, the web that the bags are made from, methods related to their manufacture, and an apparatus for manufacturing reclosable bags that is more efficient and economical than conventional methods and devices.
While most packaging is done with polyethylene sheeting, or multilayer sheeting that includes a polyethylene layer, there are problems in sealing reclosable profiles to the such sheeting due to the thickness of the profiles, or the thickness of flange material that may be integral with the profile. Sealing is even more difficult when the sealant layer of the bag walls is something other than polyethylene, such as oriented polypropylene, for example, used in potato chip bags. An additional problem is to manufacture reclosable bags which would remain closed until opened by the user. The present invention provides apparati, methods and materials for sealing profiles to sheeting, and for making bags in an efficient and practical manner.
Prior art such as U.S. Pat. No. 4,909,017, McMahon disclose the delivery of a pair of interlocked, profiled fasteners transversely across a web of film, to be used in forming a plurality of bags. However, the McMahon disclosure is non-enabling in that fastener strips cannot be delivered as described therein. Also, the strip material shown, if sealed in the center, would be unstable due to the rib and groove design, which would rock. Similarly, the strip material is naturally curled from extrusion and distorted from being wound onto a spool.
There are at least two other major shortcomings of the McMahon '017 patent. The first shortcoming involves the impossibility of making commercially acceptable seals of the bag walls to the backside of each fastener in the bagger sealing jaws. The second shortcoming involves the window of registration required to seal the backside of the fastener to a finished bag wall during bagger cross sealing; known form fill seal and equipment cannot repeat the film draw down with the required accuracy.
Specifically, the McMahon '017 patent describes a pressure bar seal in the bagger sealing jaws that seals the outer bag material precisely to the backside of the fastener profile. Yet, it has been discovered, as indicated in Applicant's specification, that a pressure bar seal requires a stable and flat surface to properly seal. The irregular shape of the McMahon fastener profile makes this impossible. One requires heat, dwell time, and pressure to effect a commercially acceptable seal. Due to the irregular shape of the profile, it is impossible to get enough stable pressure to accomplish a commercially acceptable seal. The surface moves and gives unpredictably. If enough heat and pressure are applied for a sufficient dwell time to mash the base of the profile flat enough to seal, the profile hooks are softened and deformed, making it impossible to repeatedly use the completed bag for opening and reclosing. In addition, no bagger can draw with the accuracy the McMahon '017 patent requires, to place the second seal, in register, on the back side of the fastener profiles.
In U.S. Pat. No. 4,528,224, it has been known to manufacture reclosable fastener assembly in which a pair or even several pairs of male and female profiles interlock. In U.S. Pat. No. 4,528,224 by inventor Steven Ausnit, such a pair fastener has shown. In FIG. 2 of Ausnit, a pair of such profiles have flanges which extend between them. However, the flanges are the same thickness as the entire based of the profiles. Similarly, in U.S. Pat. No. 4,246,288, Sanborn, a pair of fastener profiles has flanges extended there between. However, in both cases the fastener profiles are not sufficiently separate so that the flanges extending between them are not relatively ragged but are flexible and are not supportive by the fastener profiles themselves. In U.S. Pat. No. 5,509,734 again, pairs of fastener profiles are shown. However, in the '734 patent, a wedge is located between the fastener profiles.
U.S. Pat. No. 4,993,844 discloses a complimentary interlock strip extruded with and mounted on strips of plastic material. Similarly, U.S. Pat. No. 5,071,689, discloses strips of extruded plastic zipper sections. However, none of the foresaid patents discloses sealing of reclosable fastener assembly to tape strips of tape are in return are sealed to or webs of bag making materials.
PCT application number 97/06062, published Feb. 20, 1997, discloses a zipper film and bag in which a reclosable bag has a reclosable refastener assembly connected to a single wall of the bag in which the film of the bag has a reclosable fastener connected to one side thereof which does not requires attachment to any other portion of the film when making the bag. This differs from the present invention in which the fasteners attached to both wall of the bag, either directly of intermediate tape material.